1. Field of the Invention
The present invention relates to a light source for a non-self-luminous display device, and more particularly to a liquid crystal display device having a light guide panel and a back light using an LED as a light source.
2. Description of the Related Art
Recently, liquid crystal display devices are widely used as display devices. Since the liquid crystal display devices are especially thin, light, and thrifty in power consumption, they are often used as display sections of portable devices.
However, since the liquid crystal display device is not self-luminous, a lighting means is required. A planar lighting unit called a “back light” is generally used as a lighting unit for the liquid crystal display device. Cold cathode discharge tubes have been used as light-emitting elements (also referred to as light sources) heretofore; recently, LEDs (light emitting diodes) are also used as light-emitting elements.
A plate-like light guide panel is provided in a back light. The light guide panel is made of translucent resin or the like, and light entering the light guide panel from a light-emitting element propagates through the light guide panel. Provided in the light guide panel are light-reflective and dispersal members such as grooves, projections, or printed materials. The light propagating through the light guide panel by these light-reflective and dispersal members goes out of the light guide panel toward the liquid crystal display device side.
When an LED is used as a light emitting element, an FPC (Flexible Printed Circuit) for supplying power to the LED is required. To make the width of a frame of a back light (the width of a non-light-emitting area) smaller, it is required that a portion of the FPC be overlaid on the light guide panel. When the FPC is overlaid on the light guide panel, however, there arises a problem that a color of the FPC is mixed with colors on a screen. In response to the above problem, a configuration in which a light blocking material is provided on an FPC is disclosed, for instance, in JP-A-2005-251687.